Cranked rod pump apparatus and method

ABSTRACT

An improved apparatus and method are provided, for pumping fluids, such as water and/or hydrocarbons, from a subterranean formation or reservoir, through use of a cranked rod pumping (CRP) apparatus for imparting reciprocating substantially vertical motion to a rod of a sucker-rod pump having a pump stroke. The CRP apparatus includes a motor driven cranked mechanical actuator arrangement. The cranked mechanical actuator arrangement includes a substantially vertically moveable member attached to the rod of the sucker-rod pump for imparting and controlling vertical motion of the rod of the sucker-rod pump. The actuator arrangement may include pneumatic counterbalancing.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a continuation-in-part of co-pending U.S.patent application Ser. No. 12/251,789, filed Oct. 15, 2008, and claimsthe benefit of U.S. Provisional Patent Application No. 60/979,986, filedOct. 15, 2007, the entire teachings and disclosures of which areincorporated herein by reference thereto.

FIELD OF THE INVENTION

This invention relates to pumping of fluids, such as water and/orhydrocarbons, from subterranean formations or reservoirs, and moreparticularly to a pumping apparatus and method for use in such pumpingapplications.

BACKGROUND OF THE INVENTION

For many years, the familiar “horsehead” walking-beam type mechanism hasbeen used for pumping fluids such as water and/or oil from subterraneanformations. As discussed at length in commonly assigned co-pending U.S.patent application Ser. No. 11/761,484, titled “Linear Rod PumpApparatus And Method,” by Beck et al., conventional walking beamapparatuses have a number of disadvantages, not the least of which istheir large size. In addition, performance of the walking beam pumpapparatus is largely a function of the design in connection of a numberof mechanical parts, which include massive counter-weights and complexdrive mechanisms which are difficult to control for obtaining maximumpumping efficiency or to compensate for changes in the condition of thewell over time.

Also, for potential well sites in very remote locations, andparticularly in locations without access to a power grid and nopractical road access for regularly servicing a pumping apparatus or amotor generator, batteries, or other traditional stand-alone powersource for a pumping apparatus, it has heretofore been impractical, andin some cases impossible, to utilize a conventional walking-beamapparatus or other known types of prior pumping apparatuses and methods.As a result, potentially valuable energy resources have remaineduntapped.

Although the linear rod pump apparatus and methods, disclosed in theabove-referenced '484 to Beck, provide significant improvement overother prior pumping apparatuses and methods in many pumpingapplications, the continually reversing motor utilized in the linear rodpump apparatus and methods disclosed in Beck '484 may not be desirablein some pumping applications. For such applications, another type ofapparatus and method which could operate without continually reversingthe motor might prove to be more desirable.

It is particularly desirable to provide such an improved apparatus andmethod for pumping fluid from hydrocarbon wells, or other fluidreservoirs, which are located so remotely from any source of line poweror access roads that the only convenient source of energy for poweringthe pumping apparatus in an unattended mode would be a solar array. Itis particularly desirable, in this regard, for some applications to havethe solar array be the sole source of power, without the need forreliance upon any back-up batteries or other capacitive energy storage.

BRIEF SUMMARY OF THE INVENTION

The invention provides an improved apparatus and method for pumpingfluids, such as water and/or hydrocarbons, from a subterranean formationor reservoir, through use of a cranked rod pumping (CRP) apparatus forimparting reciprocating substantially vertical motion to a rod of asucker-rod pump having a pump stroke. A CRP apparatus, according to theinvention, includes a motor driven cranked mechanical actuatorarrangement. The cranked mechanical actuator arrangement includes asubstantially vertically moveable member attached to the rod of thesucker-rod pump for imparting and controlling vertical motion of the rodof the sucker-rod pump.

The cranked mechanical actuator arrangement may include a frame having abase thereof which is adapted for attachment to the wellhead of thewell. The frame further includes at least two linear guide railsextending vertically upwardly from the base when the base is attached tothe wellhead. The vertically moveable member is slideably mounted on thelinear guides and constrained by the guides for substantially linearreciprocating vertical movement along the guides.

In some forms of the invention, the cranked mechanical actuatorarrangement may further include a crank element and an articulating linkelement. The crank element is operatively coupled at a first attachmentpoint thereof to the rotatable element of the motor for rotation in afixed drive ratio with the rotatable element of the motor. In some formsof the invention, the mechanical actuator arrangement may also include adrive arrangement operatively connect between the rotatable element ofthe motor in the first attachment point of the crank element, such thatthe crank element rotates at a different speed than the rotatableelement of the motor in a fixed drive ratio. The articulating link ofthe cranked mechanical actuator arrangement may have first and secondattachments thereof, disposed at a spaced relationship from one anotheralong the articulating link element. The first attachment point of thearticulating link element may be pivotably joined to the crank elementat a second attachment point of the cranked element, with the secondattachment point of the cranked element being spaced eccentrically,radially outward from the first attachment point of the cranked element.The second attachment point of the articulating link element may bepivotably attached to the vertically moveable member.

In some forms of the invention, at least one of the cranked elementand/or the articulating link element may further include an additionalattachment point for changing the stroke of the vertically moveablemember along the guides, to thereby change the pump stroke. The motorand/or the drive apparatus may be mounted on the base of the frame.

In some forms of the invention, the cranked rod mechanical actuator mayfurther include a pneumatic counterbalance arrangement operativelyconnected between the frame and the vertically moveable member. Thepneumatic counterbalance arrangement may include at least one pneumaticcylinder that is operatively connected between the base and thevertically moveable member, for storing energy during a portion of thedownward stroke of the vertically moveable member and for releasing thestored energy during a portion of a subsequent upward stroke of thevertically moveable member. In some forms of the invention, at least onepneumatic cylinder may be disposed between the vertically moveablemember and the base, to thereby provide a physically compact apparatus,and to more advantageously align the pneumatic cylinder to apply forcebetween the vertically moveable member in the base in a direct ratherthan an offset manner.

In some forms of the invention, the articulating link element may beconfigured to include an offset section thereof, to thereby enhancealignment of various moving parts of the CRP apparatus with one another.

In some forms of a CRP apparatus, according to the invention, the motorand/or gearbox are disposed on one side of one or more linear guiderails extending vertically upward from the base of the frame, and thevertically movable member being slidingly disposed on an opposite sideof the one or more linear guide rails. The crank element and thearticulating link element have respective lengths thereof, and thevertical location of the first attachment point of the crank elementabove the base of the frame is cooperatively selected so that thevertically movable member is constrained to always hang below the firstattachment point of the articulating link in any angular position of thecrank element, during operation of the CRP apparatus, in such a mannerthat gravitational force will cause the vertically movable member to beslidingly held in contact with the one or more linear guide rails as themotor is controlled to impart reciprocating motion to the verticallymovable member along the one or more linear guide rails.

The invention may also take the form of a method for constructing,installing, operating, replacing, and/or maintaining a CRP apparatus inaccordance with the invention. In one form of the invention, a method isprovided for extending the life of a hydrocarbon well having a walkingbeam apparatus operatively connected thereto for imparting reciprocatingsubstantially vertical motion to a rod of a sucker-rod pump having astroke disposed in the well, by disconnecting the rod from thewalking-beam apparatus and operatively connecting the rod to a CRPapparatus according to the invention.

A method for replacing a walking beam apparatus with a CRP apparatus,according to the invention, may further include operating the CRPapparatus at a slower stroke rate than the stroke rate of the walkingbeam pump prior to its replacement by the CRP apparatus. The method,according to the invention, may include mounting the CRP apparatusdirectly on a wellhead of the well, to thereby preclude the need for aseparate mounting structure for the CRP apparatus. A method, accordingto the invention, may also include leaving the walking beam apparatus inplace adjacent to the well, after installation of the CRP apparatus.

A CRP apparatus, according to the invention, may also include a motordrive and controller for operating the motor in a substantially constantinput power operational mode. The CRP apparatus may be configured toinclude substantially no electrical power storage elements. In somecases, where the inertia of the rotatable element of the motor isinsufficient to maintain a constant input power without excessive speedvariations, additional inertia may be added to rotatable element of themotor.

A CRP apparatus or method, according to the invention, may includeoperatively coupling a solar energy power source to a CRP apparatus,according to the invention, for providing some or all of the power fordriving the motor. In some forms of the invention, the CRP solar energypower source is the sole source of power for driving the motor, suchthat the CRP apparatus only pumps when the solar energy power source isproducing sufficient power to drive the motor. Those having skill in theart will recognize that the capability of the invention to be practicedsolely with a solar energy power source without the need for anyelectrical power storage elements, makes apparatuses and methods,according to the invention, particularly desirable for use in remotelocations having little or no access to power lines or maintenanceroads.

The invention may also take the form of a method for pumping fluid froma source of fluid located in a remote location, by operatively attachinga CRP apparatus, according to the invention, to the source of the fluid.The method may further include attaching the CRP apparatus to astand-alone source of power, such as an engine driven generator, abattery, or a solar collecting array. In some forms of the invention,the stand-alone source of power is a solar energy power source.

Some forms of a method, according to the invention, may further includeproviding the source of fluid at the remote location. Where the sourceof fluid at the remote location is a fluid well, a method according tothe invention may further include providing the fluid well through stepssuch as drilling the well, and/or uncapping an existing abandoned well.

Other aspects, objects and advantages of the invention will be apparentfrom the following detailed description of the accompanying drawings,photographs and other attachments.

BRIEF DESCRIPTION OF THE DRAWINGS AND ATTACHMENTS

The accompanying drawings and attachments incorporated in and forming apart of the specification illustrate several aspects of the presentinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a schematic illustration of a first exemplary embodiment of acrank rod pumping apparatus (CRP), according to the invention, mountedto the wellhead of a hydrocarbon well.

FIG. 2 is a schematic illustration of the first exemplary embodiment ofthe CRP pumping apparatus, according to the invention, mounted on thewellhead of the well shown in FIG. 1, and operatively connected forpumping fluid from the well, instead of the walking beam apparatus, withthe CRP pumping apparatus and walking beam pumping apparatus being drawnto the same scale to illustrate the substantial reduction in size andcomplexity of the CRP pumping apparatus, according to the invention, ascompared to the walking beam apparatus which was providing similarpumping output.

FIGS. 3 and 4 are perspective illustrations of a second exemplaryembodiment of a CRP apparatus, according to the invention.

FIGS. 5-7 are schematic illustrations of the construction of severalalternate embodiments of a pneumatic counterbalance arrangement,according to the invention.

FIGS. 8-10 are schematic illustrations showing additional constructiondetails and demonstrating the operation of several alternate embodimentsof pneumatic counterbalance arrangements, according to the invention.

FIGS. 11-13 are perspective illustrations of a third exemplaryembodiment of a cranked rod pump apparatus, according to the invention.

FIGS. 14-16 are perspective illustrations of a fourth exemplaryembodiment of a cranked rod pumping apparatus, according to theinvention.

FIG. 17 is a perspective illustration of a fifth exemplary embodiment ofa cranked rod pumping apparatus, according to the invention.

FIGS. 18 and 19 are side views of the fifth exemplary embodiment of acranked rod pumping apparatus shown in FIG. 17, with FIGS. 18 and 19showing elements of the cranked rod pump in two different positionsduring a cranking cycle of the cranked rod pump, according to theinvention.

While the invention will be described in connection with certainpreferred embodiments, there is no intent to limit it to thoseembodiments. On the contrary, the intent is to cover all alternatives,modifications and equivalents as included within the spirit and scope ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic illustration showing an embodiment of a crankedrod pump (CRP) apparatus 100 attached to a wellhead of a hydrocarbonwell. As shown in FIG. 1, the invention may be practiced with a varietyof power sources including a solar array 101 or through attachment to aconventional power grid 103.

FIG. 2 illustrates the manner in which a CRP apparatus 100, according tothe invention, may be utilized to great advantage for replacing aconventional walking beam pumping apparatus 50. In FIG. 2, the crankedrod pumping apparatus 100 is mounted on the well head 54 of ahydrocarbon well 56.

Returning to FIG. 1, the well includes a casing 60 which extendsdownward into the ground through a subterranean formation 62 to a depthsufficient to reach an oil reservoir 64. The casing 60 includes a seriesof perforations 66, through which fluid from the hydrocarbon reservoirenter into the casing 60, to thereby provide a source of fluid for adown-hole pumping apparatus 68, installed at the bottom of a length oftubing 70 which terminates in an fluid outlet 72 at a point above thesurface 74 of the ground. The casing 60 terminates in a gas outlet 76above the surface of the ground 74.

The down-hole pumping apparatus 68 includes a stationary valve 78, and atraveling valve 80. The traveling valve 80 is attached to a rod string82 extending upward through the tubing 70 and exiting the well head 54at the polished rod 52. Those having skill in the art will recognizethat the down-hole pumping apparatus 68, in the exemplary embodiment ofthe invention, forms a traditional sucker-rod pump arrangement forlifting fluid from the bottom of the well 56 as the polished rod 52imparts reciprocal motion to rod string 82 and the rod string 82 in turncauses reciprocal motion of the traveling valve 80 through a pump stroke84. In a typical hydrocarbon well, the rod string 82 may be severalthousand feet long and the pump stroke 84 may be several feet long.

As shown in FIG. 1, the first exemplary embodiment of a cranked rod pumpapparatus 100, according to the invention, includes a cranked mechanicalactuator arrangement 102, a motor 104, and a control arrangement 106,with the control arrangement 106 including a controller 108 and a motordrive 110. A controller and/or motor drive, according to the invention,may take a variety of forms and include some or all of the apparatusesand methods disclosed in commonly assigned: U.S. Pat. No. 7,168,924 B2,to Beck et al., titled “Rod Pump Control System Including ParameterEstimator”; and co-pending, U.S. patent application Ser. No. 11/380,861,titled “Power Variation Control System for Cyclic Loads,” to Peterson.The disclosures, teachings and suggestions of the Beck '924 patent andthe Peterson '861 patent application are incorporated herein in theirentireties by reference.

In all forms of the invention, the velocity and torque of the motor arecalculated from measurements of motor voltages and currents. Crankvelocity and torque are calculated allowing for the ratio of the gearbox. Position of the crank is determined by integrating the crankvelocity starting from a known reference position. The reference may bedetermined from a reference switch or by analyzing the pattern of thecrank torque throughout the rotation of the crank. Estimating thereference point takes advantage of the fact that the loads on the crankat the top and bottom of stroke are approximately zero and that thesetwo points are 180 degrees apart. Therefore, points in the crankrotation that have approximately zero load, but are not 180 degreesseparated from a similar point may be ignored. The position of the rodis determined by the position of the crank and the geometry of the CRPapparatus.

FIGS. 3 and 4 illustrate a second exemplary embodiment of a CRPapparatus 200, for imparting reciprocating substantially verticalmotion, as indicated by arrow 202 to a rod 204 of a sucker-rod pump,such as the one illustrated as 100 in FIG. 1, having a pump stroke 206.The exemplary embodiment of the CRP apparatus 200 includes a crankedmechanical actuator arrangement 208 having a substantially verticallymoveable member 210 attached to the rod 204 of the sucker-rod pump forimparting and controlling vertical motion of the rod 204 of thesucker-rod pump. Specifically, in the exemplary embodiment 200, the rod204 passes through a through-hole (not shown) in an upper crossbar 212of the vertically moveable member 210, and is secured to the verticallymoveable member 210 by a clamp 214 which grips the rod 204 above thevertically moveable member 210.

The first exemplary embodiment of the CRP apparatus 200 also includes amotor 216 having a rotatable element (not shown) thereof operativelyconnected in a manner described in more detail below to thesubstantially vertically moveable member 210 of the linear actuatorarrangement 208.

As shown in FIGS. 3 and 4, the crank mechanical actuator arrangement 208in the exemplary embodiment 200 of the invention includes a frame 218,having a base 220 adapted for attachment to the wellhead of a well, andtwo linear guide rails 222, 224 which extend vertically upward from thebase 220, when the base 220 is attached to wellhead. The verticallymoveable member 210 is slideably mounted, by linear bearings (not shown)on the linear guides 222, 224 and constrained by the guides 222, 224 forsubstantially linear reciprocating vertical movement along the guides222, 224 in the manner illustrated in FIGS. 3 and 4.

As shown in FIGS. 3 and 4, the exemplary embodiment of the crankmechanical actuator arrangement 208 in the exemplary embodiment of theCRP apparatus 200 includes a drive arrangement, in the form of a rightangle gear box 226, which is mounted on the base 220. The rotatableelement of the motor 216 is attached to a vertically oriented input (notshown) of the gear box 226, and converted to motion of a horizontallyoriented output shaft 228 of the gear box 226 by a gear train (notshown) within the gear box 226. In this manner, the rotatable element ofthe motor 216 is operatively coupled in a fixed-ratio drive arrangementto the output shaft 228 of the gear box. It will be further seen fromFIGS. 3 and 4 that the upper ends of the guides 222, 224 are joined byan upper frame cross member 230, and that the frame 218 further includesa motor mounting bracket 232 which extends downward from the upper framecross member 230 to provide support for the motor 216 in its verticallyoriented position atop the gear box 226.

As further shown in FIGS. 3 and 4, the crank mechanical actuatorarrangement 208 of the first exemplary embodiment 200 includes a crankelement 234 and an articulating link element 236. As will be understoodfrom FIGS. 3 and 4, the crank element 234 is operatively coupled at afirst attachment point thereof to the rotatable element of the motor216, by virtue of the above-described attachment of the motor 216 to thegear box 226, attachment of the first attachment point of the crankelement to the output shaft 228 of the gear box 226, such that the crankelement 234 rotates in a fixed drive ratio with the rotatable element ofthe motor 216.

The articulating link element 236 has first and second attachment pointsthereof, disposed at a spaced relationship from one another along thearticulating link element 236. The first attachment point of thearticulating link element 234 is pivotably joined to the crank element234 at a second attachment point of the crank element 234 which isspaced eccentrically and radially outward from the first attachmentpoint of the cranked element 234. The second attachment point of thearticulating link element is pivotably attached to the verticallymoveable member 210.

Those having skill in the art will recognize that, by virtue of theabove-described arrangement, as the motor 216 drives the output shaft ofthe gear box 226, the crank element rotates with the output shaft of thegear box, passing on part of each stroke through a slot in the base 220and causes the articulating link element 236 to drive the verticallymoveable member 210 up and down along the guides 222, 224 to therebyimpart the reciprocating pump stroke to the rod 204.

As will be noted from an examination of FIG. 4, the crank element 234,in the exemplary embodiment 200, is essentially a lever having anadditional attachment point 235 for the articulating link element 236,so that the stroke length 206 may be varied by changing the attachmentpoint to the crank element 234. It will be further noted, by thosehaving skill in the art, that although a simple lever-like configurationwas selected for use in the exemplary embodiment 200, in otherembodiments of the invention, the crank element 234 may have othershapes, such as triangular, square, or circular, and may also includeadditional attachment points to provide for a wider selection of strokelengths. It will be yet further noted, that, in other embodiments of theinvention, the articulating link element 236 may also have additionalattachment points for use in adjusting stroke length.

As shown in FIGS. 3 and 4, the cranked rod mechanical actuator 208 ofthe exemplary embodiment of the CRP apparatus 200 also includes apneumatic counterbalance arrangement 238, which includes four pneumaticcylinders 239 operatively connected between the frame 218 and thevertically moveable member 210, in addition to other components whichare operatively connected in a suitable manner, such as those describedin greater detail below hereto. As will be understood, from a review ofthe drawings and description given herein, the exemplary embodimentpneumatic counterbalance arrangement 238 in the CRP apparatus 200includes several pneumatic cylinders 239 operatively connected betweenthe base 220 and the vertically moveable member 210 for storing energyduring a portion of the downward stroke of the vertically moveablemember 210, and for releasing the stored energy during a portion of asubsequent upward stroke of the vertically moveable member 210. Additionof the pneumatic counterbalance arrangement 238 results in the liftingforce available from the CRP apparatus being increased substantiallyover the lifting capacity of a CRP apparatus, according to theinvention, which does not include the pneumatic counterbalancearrangement 238.

In some cases, the available power, due to limitations in the powersource, electronic drive rating or mechanical limitations of theapparatus, may not be sufficient to rotate the crank from a fullylowered, stationary position through a full rotation. In those cases,the crank is rotated in a first direction until the rotational speed ofthe motor decreases, due to loading, below some threshold. At this time,rotational direction is reversed to command torque in the second,opposite direction. During each iteration of this rocking action, energyis stored in the lifted mass of the rod string, pump and fluid column.This energy is then returned to the kinetic energy of the pump mechanismor into the pressurization of the pneumatic counterbalance system as thelifted mass is lowered. In this way, the crank pump mechanism willachieve greater and greater speed and inertia and/or the counterbalancewill support more and more of the weight of the fluid column, rod stringand downhole pump mechanism each time it passes through the fullylowered position, until the combined inertia, counterbalancing andavailable power are sufficient to rotate the mechanism through a fullcycle. From this point the mechanism continues in a single rotationaldirection.

FIG. 5 is a schematic illustration of a portion of the CRP apparatus200, illustrating the placement of a pair of pneumatic cylinders 239 ofthe pneumatic counterbalance arrangement 238 configured as shown anddiscussed above with regard to FIGS. 3 and 4. Specifically, in theconfiguration shown in FIGS. 3-5, the rod 240 of the cylinders 239 isoperatively attached to the upper crossbar 212, and the base of thecylinders 239 is attached to the base 220 of the frame 218. Those havingskill in the art will recognize, however, that a pneumaticcounterbalance arrangement according to the invention may take a varietyof other forms, such as those illustrated schematically in FIG. 6 andFIG. 7. In FIG. 7, the cylinders 239 are mounted on the upper framecross member 230 with the rods 240 of the cylinders 239 extendingdownward into operative contact with the upper crossbar 212. FIG. 7illustrates an alternate placement of the cylinders 239 between theupper frame cross member and the moveable upper crossbar 212.

It is contemplated that, in addition to alternate mounting arrangementsfor the pneumatic cylinders 239, the number of cylinders utilized in anygiven application may also be greater or less than that shown in FIGS.3-7, in various embodiments of the invention. It is also contemplatedthat it will generally be advantageous to have a working axis of thecylinders 239 aligned as closely as possible with the polished rod 204,so that the counterbalance forces generated by the cylinders areoperatively transmitted as directly as possible to the polished rod 204.

FIGS. 8-10 are schematic illustrations of several alternate embodimentsof a pneumatic counterbalance arrangement 238, according to theinvention. It will be recognized that the embodiments shown in FIGS.8-10 are illustrative of the general principles of construction andoperation of a pneumatic counterbalance arrangement according to theinvention but are by no means intended to be limiting. Those havingskill in the art will recognize that there are many other ways ofconstructing and operating a pneumatic counterbalance arrangement withinthe contemplated scope of the invention. It is further noted that theembodiments shown in FIGS. 8-10 all operate on a “bootstrap” principle,in which air is drawn into the cylinder 239 and trapped in a volumebelow a piston 242 of the cylinder 239 by virtue of reciprocatingmovements imparted to the rod 240 of the cylinder 239 by upward movementof the upper crossbar 212 in combination with the operation of an inletcheck valve 244. Repetitive cycling of the piston 242 up and downresults in a counterbalance pressure being built up on the cylinder 239below the piston which then exerts an upward force on the piston 242which is transmitted through the rod 240 as an upward counterbalancingforce against downward movement of the upper crossbar 212. Thisresultant counterbalancing force acts against the weight of the rod andpumping mechanism on the downward stroke of the pump and further acts toassist the CRP apparatus in pulling the rod 204 upward on a successivestroke.

In the embodiment shown in FIG. 8, as the rod 240 pulls the piston 242upward on an upward stroke of the CRP apparatus 200, the inlet checkvalve 244 opens and allows a flow of air into the cylinder 239 in alower chamber having a volume defined by the space between the piston242 and the inlet check valve 244. When the piston 242 reaches the topof its stroke and begins to move downward on its downward stroke, thecheck valve 244 closes and traps the ingested air between the piston 242and the inlet check valve 244. As the piston 242 continues to movedownward, the space between the piston 242 and the inlet check valve 244becomes smaller, which causes the pressure of the air trapped betweenthe piston 242 and the inlet check valve 244 to increase. This increasein pressure results in a storage of energy which is then released on thesuccessive upstroke as the piston 242 moves upward to thereby generatethe counterbalancing force aiding the CRP apparatus in raising the rod204 on its upstroke. As a practical matter, with the arrangement shownin FIG. 8 it may take a rocking action as described above to allow thepressure between the piston 242 and the check valve 244 at the bottom ofthe pump stroke 206 to “bootstrap” up to a maximum working value. Theinlet check valve 244 will continuously open to replenish any airleaking past the piston 242 during operation of the CRP apparatus. Inthe embodiment of FIG. 8, the cylinder 239 may be either a single actingor a double acting cylinder.

The exemplary embodiment of the pneumatic counterbalance arrangement 238shown in FIG. 9 is essentially identical to the embodiment shown in FIG.8 and described above, with the exception that in the embodiment of FIG.9 the pneumatic counterbalance arrangement 238 also includes an outletcheck valve 246 and the cylinder 239 is a double acting cylinder.Operation of the embodiment shown in FIG. 9 is essentially the same asoperation of the previously described embodiment of FIG. 8, with theexception of the action of the outlet check valve 246. As will beunderstood from an examination of FIG. 9, whereas the inlet check valve244 is configured to allow air to be drawn into the cylinder 239 as thepiston moves upward and to close and trap air between the piston 242 andthe inlet check valve 244 on the downward stroke of the piston, theoutlet check valve 246 is configured to allow air to exit the spacebetween the piston 242 and the outlet check valve 246 as the piston 242moves upward, and prevent entry back into the space between the piston242 and the outlet check valve 246 as the piston 242 moves downward. Byvirtue of this arrangement, as the piston 242 is reciprocated within thecylinder 239, in addition to pressure being built up in the space belowthe piston 242 pressure above the piston 242 is reduced belowatmospheric as the piston 242 is forced downward by the action of theupper crossbar 212 on the piston rod 240. This arrangement provides anadvantage in that the embodiment of FIG. 9 generates a greater pressuredifferential and resultant counterbalancing force across the piston 242than is generated in the embodiment shown in FIG. 8.

FIG. 10 illustrates yet another alternate embodiment of a pneumaticcounterbalance arrangement 238, according to the invention. In simpleterms, the embodiment shown in FIG. 10 combines a cylinder 239 havinginlet and outlet check valves 244, 246 arranged in operating asdescribed above with regard to the embodiment of FIG. 9, with anadditional pumping cylinder 248 having a configuration and operationsimilar to that described above with regard to the embodiment of FIG. 8.

The pumping cylinder 248 includes a piston 250 driven by a piston rod252 which is operatively connected to the upper crossbar 212 to operatesubstantially in a parallel manner to the piston rod 240 of the piston239. A second inlet check valve 254 is provided to allow air to be drawninto both the cylinder 248 and the cylinder 239 beneath their respectivepistons 250 and 242 on a first upstroke of the CRP apparatus 200. Onsubsequent upstrokes, the pressure in reservoir cavity 256 would exceedthe pressure in pumping cavity 258, causing check valve 244 to remainclosed. On a downward stroke of the CRP apparatus 200, the pistons 242and 250 compress the air in the pumping cavity 258 and the reservoircavity 256. As the air in the pumping cavity 258 compresses, it willexceed atmospheric pressure, causing inlet check valve 254 to close. Theair in the pumping cavity 258 will continue to compress and, due to itsrelatively smaller volume, will compress to a higher pressure than theair in the reservoir cavity 256. When this occurs, check valve 244 willopen and allow the higher pressure air to enter the reservoir cavity256. As the CRP apparatus 200 reciprocates, the reciprocal motion of thepistons 242 and 250 results in pressure above atmospheric being built upin the reservoir cavity 256. By raising the pressure at the inlet to thefirst inlet check valve 244 above atmospheric, a higher counterbalancepressure may be built up in the reservoir cavity 256 of the embodimentshown in FIG. 10 than can be achieved with the embodiments of FIG. 8 andFIG. 9 in which the pressure upstream of the inlet check valve 244 islimited to atmospheric pressure. It will also be appreciated that thepressure generated in the pumping cavity 258 will contribute to thecounterbalance effect and be transmitted through the rod 252 of thepumping cylinder 248 to the upper crossbar 212. As a practical matter,with the arrangement shown in FIG. 10 it may take several strokes of theCRP apparatus 200, or a rocking action as described above, to allow thepressure between the piston 242 and the check valve 244 at the bottom ofthe pump stroke 206 to “bootstrap” up to a maximum working value.

As shown in FIG. 10, it may be desirable to add an air tank 260 at anappropriate position within a pneumatic counterbalance arrangementaccording to the invention, in order to improve operation. It may alsobe advantageous to provide some form of pressure gage or sensor 262 atan appropriate location for monitoring and controlling operatingpressures in the reservoir cavity 256, the pumping cavity 258, and thecavity between the piston 242 and the outlet check valve 246 using acontroller 264. It will be recognized that the controller 264 may takeany appropriate form, including manual or automatic controls.

FIGS. 11-13 illustrate a third exemplary embodiment of a CRP apparatus300, in accordance with the invention. The third exemplary embodiment ofthe CRP apparatus 300 is substantially identical to the second exemplaryembodiment of the CRP apparatus 200, described above, with the exceptionthat the third exemplary embodiment of the CRP apparatus 300 does notinclude a pneumatic counterbalance arrangement. FIGS. 11-13 illustratean upper crossbar 312, an articulating link element 336, and a crankelement 334 of the third exemplary embodiment of the CRP apparatus 300in different positions during a pump stroke 306.

FIGS. 14-16 illustrate a fourth exemplary embodiment of a CRP apparatus400, according to the invention. The construction of the fourthexemplary embodiment of the CRP apparatus 400 is similar in mostrespects to the embodiments described hereinabove. The primarydifference between the fourth exemplary embodiment 400 and the previousexemplary embodiments lies in mounting the motor 416 and right anglegear box 420 on top of the upper frame cross member 430 of the frame418, rather than mounting the motor and gear box 216 and 226 to the base220 of the frame 218 in the second and third exemplary embodiments ofthe CRP apparatus 200, 300. FIGS. 14-16 show a vertically moveablemember 410, a crank element 434 and an articulating link element 436 ofthe CRP apparatus 400 in several different positions during a pumpstroke 406.

FIGS. 17-19 illustrate a fifth exemplary embodiment of a CRP apparatus500, according to the invention. The construction of the fifth exemplaryembodiment of the CRP apparatus 500 is similar in many respects to theother embodiments of CRP apparatuses described hereinabove. The primarydifference between the fifth exemplary embodiment 500 and the previousexemplary embodiments lies in mounting the motor 516 and right anglegear box 526 on one side of a vertical guide rail member 519, of theframe 518, having one or more linear guide rails 522, 524 on an oppositeside of the guide rail member 519 from the motor 516 and gearbox 526 forguiding a vertically movable member 510 along the linear guide rails522, 524. The vertically movable member 510 is operatively connected bya crank element 534 and an articulating link element 536 and the rightangle gearbox 520 to a rotatable element of the motor 516, in the formof a motor output shaft (not shown). By virtue of this arrangement, therotatable element of the motor 516 and the vertically movable member 510are operatively connected in a fixed relationship to one another.

FIGS. 18 and 19 respectively show the vertically moveable member 510, atthe low end and the high end of a pump stroke 506 of the CRP apparatus500. The respective lengths of the crank element 534 and an articulatinglink element 536 of the CRP apparatus, and the vertical location of theright angle gearbox 526 above a base 520 of the frame 518 arecooperatively selected so that the vertically movable member 510 willalways hang below the upper end of the articulating link 536 in anyangular position of the crank element 534, during operation of the CRPapparatus 500. As a result having the vertically movable member 510always hang below the upper end of the articulating link 536 in anyangular position of the crank element 534, in combination withpositioning the gearbox 526 and vertically movable member 510 onopposite sides of the vertical guide rail member 519, gravitationalforces will cause the vertically movable member 510 to be slidingly heldin contact with the linear guide rails 522, 524 of the vertical guiderail member 519, as the motor 516 is controlled to impart reciprocatingmotion to the vertically movable member 510 along the linear guide rails522, 524.

As best seen in FIG. 17, the pump rod 504 extends slidingly through andis secured to the vertically movable member 510 in the exemplaryembodiment of the CRP apparatus by a clamp 514 located above thevertically movable member 510, in the same manner as described above inrelation to other embodiments of the invention. As further shown in FIG.17, the vertically movable member 520 of the CRP apparatus 500 includesbearing arrangements, roller bearing arrangements 511, for reducingfrictional contact of the vertically movable member 510 with the linearguide rails 522, 524.

It will be understood that a pneumatic counterbalance arrangement,according to the invention may also be used in a CRP apparatus similarto the fifth exemplary embodiment of the invention, in other embodimentsof the invention.

All references, including publications, patent applications, and patentscited herein are hereby incorporated by reference to the same extent asif each reference were individually and specifically indicated to beincorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) is to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

What is claimed is:
 1. A cranked rod pumping (CRP) apparatus, forimparting reciprocating substantially vertical motion to a polished rodof a sucker-rod pump having a pump stroke, the CRP apparatus comprising:a cranked mechanical actuator arrangement, having a substantiallyvertically movable member attached to the rod of the sucker-rod pump forimparting and controlling vertical motion of the rod of the sucker-rodpump, the cranked mechanical actuator arrangement further includes, aframe, a crank element and an articulating link element such that theframe has a base thereof adapted for attachment to the wellhead of awell, and having one or more linear guide rails extending verticallyupwardly from the base when the base is attached to the wellhead, withthe vertically movable member being slidably mounted on the linearguides and constrained by the guides for substantially linearreciprocating vertical movement along the linear guide rails; and amotor having a right angle gear box with a rotatable element thereofoperatively connected to the substantially vertically movable member ofthe linear mechanical actuator arrangement in a manner establishing afixed relationship between the rotational position of the rotatableelement of the motor and the vertical movement of the vertically movablemember, with the crank element being operatively coupled at a firstattachment point thereof to the rotatable element of the motor forrotation in a fixed drive ratio with the rotatable element of the motor,with the motor being disposed on one side of the one or more linearguide rails above the base of the frame, and the vertically movablemember being slidingly disposed on an opposite side of the one or morelinear guide rails; the articulating link element has first and secondattachment points thereof disposed at a spaced relationship from oneanother along the articulating link element, with the first attachmentpoint of the articulating link element being pivotably joined to thecrank element at a second attachment point of the cranked element spacedeccentrically radially outward from the first attachment point of thecranked element with the second attachment point of the articulatinglink element being pivotably attached to the vertically movable member,with the crank element and the articulating link element havingrespective lengths of the CRP apparatus, and the vertical location ofthe first attachment point of the crank element above the base of theframe being cooperatively selected so that the vertically movable memberis constrained to always hang below the first attachment point of thearticulating link in any angular position of the crank element duringoperation of the CRP apparatus, in such a manner that gravitationalforce will cause the vertically movable member to be slidingly held incontact with the one or more linear guide rails as the motor iscontrolled to impart reciprocating motion to the vertically movablemember along the one or more linear guide rails.
 2. The CRP apparatus ofclaim 1, further comprising, a motor drive and controller for operatingthe motor in a substantially constant input power operational mode. 3.The CRP apparatus of claim 2, wherein, the CRP apparatus includessubstantially no electrical power storage elements.
 4. The CRP apparatusof claim 2, wherein, the CRP apparatus includes substantially no powerstorage elements.
 5. The CRP apparatus of claim 1, wherein, the CRPapparatus includes a solar energy power source operatively attached forproviding some or all of the power for driving the motor.
 6. The CRPapparatus of claim 5, wherein, the CRP solar energy power source is thesole source of power for driving the motor, such that the CRP apparatusonly pumps when the solar energy power source is producing sufficientpower to drive the motor.
 7. The CRP apparatus of claim 1, wherein,cranked rod mechanical actuator further comprises a pneumaticcounterbalance arrangement operatively connected between the frame andthe vertically movable member.
 8. The CRP apparatus of claim 7, wherein,the pneumatic counterbalance arrangement comprises, at least onepneumatic cylinder operatively connected between the frame and thevertically movable member for storing energy during a portion of thedownward stroke of the vertically movable member, and for releasing thestored energy during a portion of a subsequent upward stroke of thevertically movable member.
 9. The CRP apparatus of claim 8, wherein, theat least one pneumatic cylinder is disposed between the verticallymovable member and the base.
 10. The CRP apparatus of claim 1, wherein,at least one of the cranked element and the articulating link elementfurther comprises an additional attachment point, for changing thestroke of the vertically movable member along the guides, to therebychange the pump stroke.
 11. The CRP apparatus of claim 1, wherein, thecranked rod mechanical actuator further comprises a drive arrangementoperatively connected between the rotatable element of the motor and thefirst attachment point of the crank element.